it has 2 output channel, but no known hardware using this feature for stereo sound.
later hardware paired this with external bankswitching logic, but its logic is not emulated now in current furnace revision.
Allumer one is just rebadged Seta's thing for use in their arcade hardwares.
It has 16 channels, and all channels can be switchable to PCM sample or wavetable playback mode.
Wavetable needs to paired with envelope, this feature is similar as AY PSG but it's shape are stored at RAM: it means it is user-definable.
In furnace, this chip is can be configurable for original arcade mono output or stereo output - its simulates early 'incorrect' emulation on some mono hardware but it is also based on the assumption that each channel is connected to each output.
This chip supports 2 type waveforms, needs to paired external 8KB RAM for use these feature:
One is signed 8 bit mono waveform, its operated like other wavetable based sound systems.
These are stored at bottom half of RAM at common case.
Another one ("Envelope") is 4 bit stereo waveform, its multiplied with above and calculates final output, Each nibble is used for each output channels.
These are stored at upper half of RAM at common case.
Both waveforms are 128 byte fixed size, its freely allocated at each half of RAM except channel register area: each half can be stored total 32/31 waveforms at once.
